1. Field of the Invention
This invention relates to x-ray imaging systems and to x-ray sensors for use in such systems.
2. Discussion of Related Art
U.S. Pat. No. 5,053,582 to Cox et al discloses the details of an x-ray imaging system and both a direct conversion solid state x-ray sensor and an x-ray sensor which uses a scintillator to convert x-ray band radiation into visible light. The entire disclosure of U.S. Pat. No. 5,053,582 is incorporated herein by reference.
FIG. 16 of the Cox et al. patent shows a unique configuration for an x-ray detector in which a scintillator is positioned in a sandwich structure between a layer containing sensor elements and a layer containing preprocessors. The outputs are taken from the sensors and passed through bump bonds extending through the scintillator to the preprocessors. This configuration has many advantages, However, it would be preferable if such a sandwich structure could be produced in which the sensors and preprocessors could be closer together.
Recently, optical detectors have been developed with MOS capacitors in an epitaxial layer on a substrate, in which the substrate has been thinned so that visible light can be detected by backlighting the detectors from the substrate side rather than illuminating the MOS capacitors directly. This type of detector is discussed, for example, in "Optimizing charge-coupled detector operation for optical astronomy" by Robert W. Leach, Optical Engineering, 26(10), pgs. 1061-1066, October 1987.